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Centre Number

Candidate Number

TIME1 hour.

INSTRUCTIONS TO CANDIDATES

Write your Centre Number and Candidate Number in the spaces provided at the top of this page.You must answer the questions in the spaces provided.Do not write outside the boxed area on each page or on blank pages.Complete in black ink only. Do not write with a gel pen.Answer all nine questions.

INFORMATION FOR CANDIDATES

The total mark for this paper is 70.Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question.Quality of written communication will be assessed in Question 3.

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Double Award Science: BiologyUnit B1Higher Tier

[GDW12]WEDNESDAY 26 FEBRUARY 2020, MORNING

General Certificate of Secondary Education2019–2020

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1 (a) The photograph below shows a white rhino with a crow on its back.

Read the passage below and answer the questions that follow.

White rhinos live in the grasslands of Africa.Grass is the main food for a white rhino.The crow on the rhino’s back is feeding on ticks.Ticks are tiny animals that feed on the rhino’s blood and irritate its skin.

crow

Crow © Colin Vamdell / Science Photo LibraryRhino © Tony Camocho / Science Photo Library

Use the information and photograph above to help answer the following questions.

(i) Give the habitat of the white rhino.

[1]

(ii) Draw a food chain containing the four organisms given in the passage.

[3]

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(iii) What benefit do crows give the white rhino?

[1]

(iv) What benefit does the white rhino give the crow?

[1]

(b) In 2014 the number of white rhinos in the wild was 20 000.During this year, 6% of the white rhino population was killed by illegal hunting.

(i) Use the information given above to calculate the number of white rhinoswhich were killed by illegal hunting in 2014.

Show your working.

[2]

(ii) Give one biotic factor, that could affect the white rhino population in thewild, apart from illegal hunting.

[1]

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2 (a) Commercially prepared baby food often contains enzymes.These enzymes start to digest the baby food before it goes into a baby’s stomach.This helps a baby to completely digest its food.

(i) Name the enzyme that would be added to commercially prepared baby foodto help digest protein.

[1]

(ii) Use your knowledge of enzymes to explain why a different enzyme wouldnot digest protein.

[2]

(b) The diagram below represents part of a protein molecule.

(i) Name the type of biological molecule, represented by the different shapes inthe diagram, that make up a protein molecule.

[1]

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(ii) In the space below, draw the products formed when this part of a proteinmolecule is completely digested.

[2]

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3 Describe how microorganisms carry out decomposition.

Include the following in your answer:

• the two types of microorganism that carry out decomposition.• the process of decomposition.

In this question you will be assessed on your written communication skills, including the use of specialist scientific terms.

[6]

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4 (a) Scientists carried out an investigation into the amount of sweat lost by an athlete during 60 minutes of exercise.They recorded the volume of sweat he produced every 10 minutes during the exercise.

The graph below shows the results.

0

100

200

300

400

500

600

10 20 30 40 50 60

Time/minutes

Volu

me

of s

wea

t pro

duce

d/cm

3

0×

×

×

×

×

×

×

Use the graph to answer the following questions.

(i) Give the volume of sweat produced by the athlete over the first 30 minutes.

cm3 [1]

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(ii) Calculate the volume of sweat produced by the athlete over the second30 minutes.

Show your working.

cm3 [2]

(iii) Using your answers to (i) and (ii), calculate the difference in the volume ofsweat produced by the athlete over the second 30 minutes compared to thevolume of sweat he produced over the first 30 minutes.

cm3 [1]

(iv) The volume of sweat produced by the athlete over the second 30 minutes ismore than he produced over the first 30 minutes.Suggest why.

[1]

(b) Describe the effect of the athlete’s exercise on the volume and concentration ofurine produced after exercise.

Volume

Concentration [2]

(c) (i) Name the organ in the body that carries out osmoregulation.

[1]

(ii) Draw a circle around the phrase below that describes what would happento the blood of this athlete if this organ did not carry out osmoregulationduring exercise.

Blood would becomeless concentrated

Blood would stay thesame concentration

Blood would becomemore concentrated [1]

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5 (a) Complete the balanced chemical equation for photosynthesis by writing in the empty boxes.

+6H2O+

[3]

(b) The rate of photosynthesis in a plant can be limited by environmental factors.

The graph below shows the effect of increasing light intensity on the rate ofphotosynthesis in a plant when placed in 0.03% carbon dioxide at 20 °C and30 °C.

0

25

50

75

100

1 2 3 4 5 6

Light intensity/arbitrary units

Rat

e of

pho

tosy

nthe

sis/

arbi

trary

uni

ts

0 7

B

A

30 °C

20 °C

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(i) Name the environmental factor that is limiting the rate of photosynthesisbetween points A and B.Explain your answer.

[2]

(ii) Use your knowledge of enzyme activity to explain the difference in the rateof photosynthesis when the temperature increased from 20 °C to 30 °C.

[2]

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6 The diagram below shows a series of stages that occurred in a previously unpolluted lake.

The lake contained a wide variety of aquatic organisms.

Excess minerals enteredthe lake.

Aquatic plants and algaegrowth increased.

Aquatic plants and algaedied.

Dead aquatic plants andalgae decomposed.

Oxygen levels in thelake fell.

Fish and other aquatic animals died.

A

B

C

D

E

F

Use the information in the diagram above and your knowledge to answer the following questions.

(a) Suggest two sources of the excess minerals in stage A.

1.

2. [2]

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(b) Give two reasons why the aquatic plants and algae died in stage C.

1.

2.

[2]

(c) Explain how the decomposition of dead aquatic plants and algae (stage D)caused stage E.

[3]

(d) Complete the table below to show the level of biodiversity in this lake beforestage A and at stage F.

Choose from low, high or no change.

Write your answers in the empty boxes.

Stage Level of biodiversity

Before A

At F

[2]

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7 (a) Nitrates must be present in soil for crop growth.

(i) Name the plant cells which absorb nitrates from the soil.

[1]

(ii) Describe and explain how these plant cells are adapted for their role inabsorbing nitrates from the soil.

[2]

(iii) Name a substance, other than nitrates, that these plant cells absorb fromthe soil.

[1]

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(b) The graph below shows the effect of the mass of nitrate fertiliser on the yield ofwheat in an area of land (hectare).

4.0

5.0

6.0

7.0

8.0

40 80 120 160 200 240

Mass of nitrate fertiliser added to the soil/kg per hectare

Yiel

d of

whe

at/to

nnes

per

hec

tare

0

×

×

×

×

× × ×

4.5

5.5

6.5

7.5

8.5

(i) Wheat plants use nitrates from soil to produce a substance which increasestheir yield.Name this substance.

[1]

(ii) Use the graph to give the least mass of nitrate fertiliser that should be addedto the soil to give the maximum yield of wheat.

kg per hectare [1]

(iii) Suggest why the yield of wheat levels off.

[2]

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(c) The diagram below shows a nitrogen cycle.

Each arrow represents a process in the nitrogen cycle.

Nitrogen in the air

Nitrate in the soil

Substance A

Producers

Consumers

Decomposing bacteria

Source: Principal Examiner

(i) Name substance A.

[1]

One type of nitrogen bacteria will increase in numbers in waterlogged soil.

(ii) Name this type of nitrogen bacteria.

[1]

(iii) On the diagram, write an X on one of the arrows to show the process thebacteria in (ii) carry out in the nitrogen cycle. [1]

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8 (a) The diagram below shows a reflex arc.

pin

A

© Barking Dog Art

(i) Draw an arrow in the box on the diagram, to give the direction of a nerveimpulse along neurone A. [1]

(ii) On the diagram, label the motor neurone using a line marked B. [1]

(iii) How many synapses are there in this reflex arc?

[1]

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A reflex arc results in a reflex action.Reflex actions are faster than voluntary actions.

(b) Give one property of reflex arcs which results in this faster speed of reaction.

[1]

The reflex arc on the page opposite shows a finger being pricked with a pin.This results in a reflex action.

(c) Suggest one advantage to a person, other than speed of reaction, of this reflexaction.

[1]

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9 A student investigated photosynthesis and respiration in two different plants, A and B. The plants were the same size.

The student used a carbon dioxide probe to measure the carbon dioxide concentration in a bell jar with no plant present.The carbon dioxide concentration in the bell jar with no plant present was four arbitrary units.The student then used the probe to measure the carbon dioxide concentration in the bell jar with a plant, after two hours at different light intensities.

The diagram below shows the set up of her experiment for each plant.

carbon dioxideprobe

plant

bell jar

hydrogencarbonateindicator

© Getty Images

The table below shows the results of her experiment for plant A and plant B.

Light intensity/arbitrary units

Carbon dioxide concentrationin the bell jar/arbitrary units

Plant A Plant B

0 22 23

4 12 9

8 8 4

12 6 3

16 4 1

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(a) Describe and explain the trend in carbon dioxide concentration in the bell jar withplant A when the light intensity increased from 0 to 12 arbitrary units.Use data to support your answer.

[4]

(b) Give the light intensity at which plant B is at its compensation point.

arbitrary units [1]

(c) Describe and explain the colour of the hydrogencarbonate indicator in the belljar with plant B at a light intensity of 16 arbitrary units.

[3]

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Permission to reproduce all copyright material has been applied for.In some cases, efforts to contact copyright holders may have been unsuccessful and CCEAwill be happy to rectify any omissions of acknowledgement in future if notified.

Examiner Number

For Examiner’suse only

QuestionNumber Marks

1 2 3 4 5 6 7 8 9

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